Nickel-Based Oxide Catalyst for Selective Cyanide Removal
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Solution Overview
Problem
Existing wastewater treatment methods are inefficient and costly for selectively removing cyanide from wastewater containing both cyanide and organic compounds, as they often require excessive materials and time due to lack of selectivity between cyanide and chemical oxygen demand (COD), and may also oxidize or hydrolyze organic compounds, making it difficult to recover them.
Innovation Solution
A process and system utilizing a nickel-based oxide catalyst in conjunction with an oxidant, such as hypochlorite, to selectively remove cyanide from wastewater, maintaining the organic compounds and reducing the need for excessive material usage by preferentially reacting with cyanide over COD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrothermal systems are used to treat cyanide, then cyanide removal is achieved, but the system becomes extremely expensive to build and operate
Solution Approach 1:
The invention changes the operating parameters from extreme hydrothermal conditions (high temperature and pressure) to milder conditions by using a heterogeneous catalyst. This allows cyanide oxidation to proceed at lower temperatures and pressures, dramatically reducing equipment costs and energy consumption while maintaining effective cyanide removal
Solution Approach 2:
The invention introduces a heterogeneous catalyst as an intermediary substance that facilitates the oxidation reaction between cyanide and oxidant. This catalyst provides an alternative reaction pathway with lower activation energy, eliminating the need for expensive hydrothermal conditions while ensuring complete cyanide destruction
2Reliability
If hydrothermal systems are used to treat cyanide, then cyanide is destroyed, but organic compounds are also oxidized or hydrolyzed, preventing their recovery
Solution Approach 1:
The heterogeneous catalyst provides local active sites that are highly selective for cyanide oxidation. The catalyst surface creates localized reaction zones where cyanide is preferentially oxidized over organic compounds, allowing selective removal of cyanide while preserving recoverable organics in the wastewater stream
Solution Approach 2:
By changing from non-selective hydrothermal oxidation to catalyst-mediated oxidation at milder conditions, the reaction selectivity is improved. The catalyst enables cyanide oxidation at lower temperatures where organic compounds remain stable, preventing their degradation and enabling potential recovery
3Reliability
If hydrogen peroxide or sulfide dioxide is used with a copper catalyst, then cyanide is removed, but COD is also reacted, requiring significantly more materials
Solution Approach 1:
The invention uses a heterogeneous catalyst that can be easily separated and reused, replacing expensive soluble copper catalysts that require continuous replenishment. The solid catalyst remains stable and active over extended periods, reducing both material costs and the quantity of oxidant needed since the catalyst is not consumed in the reaction
4Reliability
If hydrogen peroxide or sulfide dioxide is used for cyanide removal, then cyanide is treated, but remaining COD interferes with copper catalyst recovery, increasing costs
Solution Approach 1:
The heterogeneous catalyst is designed as a stable solid material that can be easily separated from the liquid wastewater stream through filtration or settling. This eliminates the need for complex recovery processes and prevents COD interference, making the system economically viable for continuous operation
Solution Approach 2:
The solid catalyst acts as an intermediary that can be physically separated from the reaction mixture. Unlike soluble copper catalysts that form complexes with COD and require sophisticated recovery systems, the heterogeneous catalyst remains in the solid phase and can be easily removed, preventing interference with recovery operations
5Reliability
If alkaline chlorination or iron precipitation is used, then cyanide is removed, but additional materials are required due to lack of selectivity and COD interference
Solution Approach 1:
The heterogeneous catalyst creates localized active sites on its surface that are highly selective for cyanide oxidation. This local selectivity ensures that the oxidant reacts preferentially with cyanide rather than COD, reducing overall material consumption and eliminating the need for additional chemicals to compensate for non-selective reactions
6Reliability
If activated carbon is used to adsorb cyanide, then cyanide is removed, but many organic compounds are also adsorbed, reducing recovery potential
Solution Approach 1:
The heterogeneous catalyst provides specific active sites on its surface that are chemically selective for cyanide oxidation. Unlike activated carbon that relies on non-specific physical adsorption, the catalyst surface creates localized chemical reactions that selectively transform cyanide while leaving organic compounds unaffected and recoverable
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process effectively reduces cyanide levels in wastewater to below acceptable limits while preserving a majority of the organic compounds, thereby reducing costs and maintaining the integrity of the treatment system, with the nickel-based oxide catalyst being inexpensive and easily replaceable, and hypochlorite showing superior selectivity for cyanide removal.
Implementation Method 1
contacting the wastewater with an amount of an oxidant in the presence of a nickel-based oxide catalyst to selectively remove an amount of the cyanide relative to the chemical oxygen demand from the wastewater
Implementation Method 2
The systems and processes utilize readily available and inexpensive materials, thereby maintaining low costs for cyanide removal. In addition, the inventors have surprisingly found the systems and processes described herein selectively remove cyanide relative to the COD in wastewaters containing both
Data Source
AI summary
There are provided systems (10) and processes for the selective removal of cyanide from a wastewater stream (12) comprising cyanide and an amount of organic compounds therein.